A number of applications currently exist within communication systems, such as those supporting Global System for Mobile Communication (“GSM”), Time Division Multiple Access (“TDMA”), Code Division Multiple Access (“CDMA”), Orthogonal Frequency Division Multiple Access (“OFDMA”) and Universal Mobile Telecommunications System (“UMTS”) technologies, for which location solutions are needed by mobile units, mobile stations, user equipment (“UE”) or other devices and by other entities in a wireless network. Examples of such applications may include, but are not limited to, GSM positioning and assisted global position system (“A-GPS”) positioning. A-GPS adaptable UE may acquire and measure signals from a number of satellites to obtain an accurate estimate of the UE's current geographic position. GPS-based solutions may offer excellent accuracy, but GPS-based solutions generally suffer from yield issues in indoor environments or in environments that provide a poor line of sight to the open sky in which to best receive GPS satellite transmissions. Furthermore, embedding GPS chipsets into UE may also add an associated cost to the manufacturing of the UE and an associated cost to A-GPS functionality in the respective communications network. Further, some organizations are hesitant to offer a positioning method solely based upon the availability of a satellite network controlled by the United States government.
There, however, exists a need in the art to locate UMTS, OFDMA or W-CDMA mobile devices to satisfy FCC E-911 regulations as well as to provide Location Based Services for mobile phone users. The 3GPP UMTS standard outlines several methods for location including Cell-ID, A-GPS, Observed Time Difference of Arrival (“OTDOA”), and Uplink (Time Difference of Arrival (“U-TDOA”). Cell-ID generally is the simplest method which provides coarse positioning of mobile devices based on a known location of the coverage area centroid of each base station sector. Additionally, A-GPS is a straightforward implementation for network and handset manufacturers due to their legacy in CDMA2000 networks. Likewise, U-TDOA is also a straightforward technique for those skilled in the art and has been widely deployed for other air standards. OTDOA, on the other hand, is confronted with significant implementation challenges for network carriers, due to the fact that the base station timing relationships must be known, or measured, for this technique to be viable. For unsynchronized UMTS networks, where the base station timing is not locked to a common timing source, the 3GPP standard offers the suggestion that base station Location Measurement Units (“LMUs”) or Network Synchronization Units (“NSUs”) may be utilized to recover this timing information. Once the base station timing relationships are measured, the handset measurements of Observed Time Difference (“OTD”) between various base stations may be translated into absolute range differences from which position can be calculated (e.g., through UE-based or UE-assisted methods).
Network carriers, however, appear to have little interest in implementing the OTDOA solution. This may be due to a general lack of cost-effective solutions for practical implementations of OTDOA in unsynchronized UMTS networks, significant hardware, installation, testing, and associated maintenance costs, and/or a lack of available LMU or NSU vendors. Further, the lack of interest by network carriers in implementing the OTDOA solution may also be due to a lack of handset manufacturers implementing OTDOA measurements into the associated firmware, negative perception of OTDOA due to the potential network capacity impacts if Idle Period Downlink (“IPDL”) is enabled by carriers, and/or carrier perception that A-GPS handsets will meet all the location needs of its users.
The UMTS standard offers alternative location solutions for UE location. OTDOA technologies, with or without IPDL, have been developed and integrated into the UMTS standard as optional features to enable location of UEs. However, UMTS carriers have been reluctant to adopt these technologies because carriers had not initially requested these optional features in most UE devices. Additionally, concern may exist regarding the impact OTDOA may have on the operation of a communications network including call quality and network capacity. Because widespread adoption of OTDOA may require modifications in both the base stations and mobile stations, network providers are generally more interested in a solution that operates with existing mobile devices and base stations.
Embodiments of the present subject matter therefore provide a novel method and system to derive OTDOA information from the existing mobile devices and base stations utilizing messages typically used for normal operation of the mobile device. For example, measurement report messages, e.g., network measurement reports, are generally utilized for managing handover. UMTS mobile devices report these messages to a base station for proper operation. These messages contain the Connection Frame Number (“CFN”)—System Frame Number (“SFN”) information between serving and neighbor nodes, such as, but not limited to, base stations, base station sectors, cells, etc. Embodiments of the present subject matter may also derive a neighboring node's SFN-SFN OTD from this information. Moreover, if the neighboring SFN times are known, OTDOAs of the neighboring node downlink, and thus the location of the UMTS device, may be determined. Embodiments of the present subject matter may therefore make it possible to determine downlink OTDOA values for mobile devices that do not support the OTDOA feature through the exploitation of network measurement reports that are generally not intended for location determination.
Accordingly, there is a need for a method and system for locating UMTS user equipment using measurement reports. Therefore, an embodiment of the present subject matter provides a method for estimating a location of a wireless device. The method comprises the steps of determining an OTDOA based solely on signals received from plural nodes and determining the OTDOA using information received from a network measurement report.
Another embodiment of the present subject matter provides a method for estimating a location of a wireless device. The method comprises the steps of determining an OTDOA based solely on signals received from plural nodes and from signals received from a satellite navigation system and determining the OTDOA using information received from a network measurement report.
A further embodiment of the present subject matter provides a method for estimating a location of a wireless device receiving signals from a plurality of nodes of a communication system. The method comprises the steps of determining a first value based on a network timing characteristic for one of the nodes and determining a second value based on a network measurement report characteristic. An OTDOA hyperbola based on the first and second values may be determined, and a location of the wireless device estimated as a function of the OTDOA hyperbola.
An additional embodiment of the present subject matter provides a method for estimating a location of a wireless device receiving signals from a serving node, a first neighboring node, and a second neighboring node, where each node is a node of a communication system. The method comprises the steps of determining a first value based on a first network timing characteristic for the first neighboring node and determining a second value based on a second network timing characteristic for the second neighboring node. A third value may be determined based on a third network timing characteristic for the serving node, and a fourth value may be determined based on a first network measurement report characteristic. A fifth value may be determined based on a second network measurement report characteristic, and an OTDOA hyperbola calculated based on at least one of the first, second, third, fourth, or fifth values. A location of the wireless device may then be estimated as a function of the OTDOA hyperbola. Alternative embodiments of the present subject matter may calculate the OTDOA hyperbola by calculating a difference between the first and second values, calculating a difference between the first and third value, or calculating a difference between the fourth and fifth values. Yet another embodiment of the present subject matter may calculate the OTDOA hyperbola by calculating a first OTDOA hyperbola based on at least one of the first or second values, and at least on one of the fourth or fifth values, and calculating a second OTDOA hyperbola based on at least one of the first or third values, and on the fourth value.
Another embodiment of the present subject matter provides a system for estimating a location of a wireless device receiving signals from a plurality of nodes of a communication system. The system may comprise circuitry for determining a first value based on a network timing characteristic for one of the nodes, and circuitry for determining a second value based on a network measurement report characteristic. The system may further comprise circuitry for calculating an OTDOA hyperbola based on the first and second values, and circuitry for estimating a location of the wireless device as a function of the OTDOA.
These embodiments and many other objects and advantages thereof will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the embodiments.